The greater amount of lead you are exposed to as a child, the dumber you get. Paint, batteries, and leaded gasoline could all be threatening a child’s cognitive potential. Preschool blood lead levels over 40 micrograms of lead per deciliter of blood lower average IQ by 15 points. Studies have also demonstrated that the neurotoxin has other adverse consequences, including hyperactivity, behavioral deficits, and learning disabilities.

Public health experts have long recognized this link between lead exposure and loss of IQ as a potential epidemic. One of the greatest large-scale public health coups in developed countries has been the decline in children’s blood levels worldwide, especially after the removal of leaded gasoline. In fact, only six countries in the world continue to use leaded gasoline.

Yet developing countries still suffer from high levels of lead exposure. A study published June 25 in Environmental Health Perspectives puts a dollar sign on the epidemic in hopes of convincing the global community to make the investment in reducing lead exposure in low- and middle-income countries. According to the head of the study, Dr. Leo Trasande of the NYU School of Public Health, “There’s ample literature that suggests that children that have lower IQs are less well able to contribute to society, and over the past decades researchers have quantified the percentage that on average is lost over a lifetime in economic productivity per IQ point.”

Applying this algorithm to developing countries, the study estimates economic losses equal to $134.7 billion in Africa, $142.3 billion in Latin America and the Caribbean, and $699.9 billion in Asia. In total, childhood lead exposure is costing low- and middle-income countries $992 billion. The conclusion: investing in lead hazard control will quickly save these third-world countries money.

Global health, unfortunately, is a number game. Trasande argues that these particular numbers ought to motivate countries and the global health community to prioritize the eradication of lead. “Many of the other interventions proposed to improve public health globally require a significant upfront investment. And literature on efforts to prevent environmental exposure such as lead suggest immediate and large payouts for intervention and a favorable cost-benefit profile,” Trasande says. “So we recognize that the global development community needs to prioritize its investments, yet our findings suggest that lead exposure prevention is highly favorable from an economic development perspective.”

But is reducing lead exposure the silver bullet? Developing countries face a plethora of obstacles holding them back from rapid economic growth. Lead exposure could simply be a symptom of a greater set of problems associated with poverty in third-world countries rather than the problem itself. Trasande argues based on a mounting set of studies from the last decade that all point to low-level lead exposure hurting cognitive potential that “with respect to environmental hazards, the evidence is greatest for causation of lead as an impact on cognitive potential.”

Indeed, a reduction in lead-exposure may be the key to solving many other societal problems. In the past, lead as a neurotoxin has been a concern not only among public health experts but also among criminologists. Remember that controversial claim Steven Levitt made in Freakonomics, where he suggested that crime dropped in the 1990s because of Roe v. Wade? Levitt and John Donohue argued that legalized abortion led to fewer unwanted children and then, a couple decades later, to fewer violent young men. Well, economic consultant Rick Nevin proposed a counter theory: as gas lead levels rose, so did violent crimes; and as the levels sank, crime rates sank. Leaded gasoline, he claimed, could be responsible for as much as 90 percent as the rise and fall of violent crime over the last century.

Trasande excluded the costs of associative criminality from his study, asserting that there is a “greater debate about the link between lead and criminality” compared to the link between lead and cognitive potential. The study writes that in the US the net benefits of lead hazard control range from $181 to $269 billion dollars, far outstripping the costs of $1.2 to $11 billion. He hopes such numbers will motivate the global community to eradicate the environmental health threat. “Each country can implement policies, but this is a shared responsibility with the global development community,” he says.

I think the brain, or "cognitive potential" is
more complicated than this article makes it out to be. In fact, lead exposure
maybe one of least impactful force on the economic growth of "third
world" countries. Most of the "evidence" in this article are
suspect, especially the appeal to I.Q. testing which its known to be
unreliable.